Sinn Fein is to bring a proposal to Northern Ireland's Assembly calling on Arlene Foster to stand aside as First Minister.
The Democratic Unionist leader has been under mounting pressure over her handling of a botched green energy scheme which critics predict will overspend by £400 million.
Sinn Fein are the DUP's partners in Government but the larger unionist party can use a parliamentary procedure to thwart any attempt to unseat her.
The DUP has said it supports an independent investigation. Sinn Fein believed an independent judicial figure from outside Northern Ireland should undertake the inquiry and raised the prospect of prosecutions if wrongdoing was uncovered.
Deputy First Minister Martin McGuinness said: "Sinn Fein will bring forward a proposal to the Assembly which calls on the First Minister to stand aside until this independent investigation brings forward a preliminary report."
He added: "The statement which Arlene Foster plans to make to the Assembly tomorrow does not have my authority or approval as deputy First Minister."
Sinn Fein's deepening estrangement from the DUP could have grave consequences for the power-sharing institutions, which are predicated upon cross-community cooperation between the two largest parties of unionism and nationalism.
A generous scheme designed to encourage businesses to switch from burning fossil fuels is now predicted to cost the taxpayer millions after inadequate cost controls over payments.
Mrs Foster's role in establishing the Renewable Heat Incentive (RHI) and during the period before it was shut down is under intense scrutiny but she has denied any wrongdoing.
A DUP statement said the party supported the need for a public and speedy independent investigation, free from partisan political interference, to establish the facts around the RHI scheme.
The row threatening the peace-building institutions has erupted over the controversial scheme which paid out subsidies well in excess of the costs of buying renewable fuel.
Claims of widespread abuse include a farmer allegedly set to pocket around £1 million in the next 20 years for heating an empty shed.
The "cash for ash" scandal reached fever pitch when former economy minister Jonathan Bell broke ranks to level a series of explosive claims against his leader and party advisers.
In an extraordinary TV interview, a tearful Mr Bell said God told him to come clean as he claimed a "highly agitated and angry" Mrs Foster demanded he keep the RHI open for an extra fortnight despite its huge losses.
Mr Bell was suspended by the party over the weekend.
The Sinn Fein intervention due to be debated at Stormont said there were serious allegations of "incompetence, corruption and abuse".
It said an independent, time-framed, robust and transparent investigation should be undertaken by an independent judicial figure from outside Northern Ireland and be appointed by the Attorney General John Larkin QC.